The present invention relates to a shock absorber device for telescopic protection devices of the type consisting of a plurality of box-shaped elements. Protection devices of this type are mainly used for the guides of automatic machines, machine tools and robots, to prevent foreign matter, such as dirt, chippings and emulsions used to cool the area machined, from entering the guide contact zone.
Scrapers, normally made of elastomer or plastics, are fitted amongst the box-shaped elements. The scrapers not only prevent foreign matter from entering the gap between two contiguous box-shaped elements, but also allow the formation of a satisfactory hermetic seal. Since the protection device is connected to the mobile part of the machine, extension of the box-shaped elements follows the speed of these mobile parts. This speed may be high and, considering the mass of the box-shaped elements, when the protection device is fully extended, a significant impact force between the box-shaped elements may be reached. Obviously, such impact must be avoided, to prevent wear on the protection device, to avoid the effects on the mobile parts of the machine and to limit the noise level.
It is, therefore, essential to fit shock absorber devices between the box-shaped elements. An example of these shock absorber devices is described in the patent for utility model DE-U-7137781. In the said document, the shock absorber device is simply obtained by applying a strip of synthetic cellular material to the rear of the scraper and the zone which makes contact with the smallest adjacent box-shaped element.
Another type of shock absorber device for the box-shaped elements of a telescopic protection device, made with a strip of synthetic material different to the scraper material is described in patent EP-B-290-822. To increase the shock absorbing effect of the shock absorber devices made of strips of synthetic material, patent EP-B-502-328 describes a shock absorber device made using a strip of elastic material with holes which increase the deformability of the strip.
However, due to the high speed of the mobile machine parts, the mass of the box-shaped elements and the limited deformability of the shock absorber devices, impact is still possible with these types of shock absorber devices.
Moreover, when such protection devices arrive at the maximum extension, the elements which form the protection devices stop, passing from a high speed to zero velocity in a very short time, and so are subject to high deceleration, which may have a damaging effect on the mobile parts of the machines.
Since these shock absorber devices are continuous along the entire perimeter of the box-shaped element, they are also relatively expensive.
The aim of the present invention is to improve the capacity for absorption of impact between the elements which form the protection device.